1. Field of the Invention
The present invention relates to a process for filling a hollow portion of a hollow filaments with filling materials composed of functional material, and more particularly to a method for filling a hollow portion of a hollow fiber of which only parts or ends are submerged in the filling materials.
2. Description of Related Art
The traditional processes of making core-sheath fiber include various composite spinning methods. In those processes, including melt-spinning or wet-spinning, a high temperature or a special solvent is necessary. However, most of functional materials, particularly drugs, fragrance, and biochemical materials, are sensitive to temperature or solvent, and such a high temperature or the solvent may affect or destroy the performance of the functional materials, as a result, the application of many kinds of functional materials is limited in the traditional spinning process. Therefore, the kinds of functional fiber produced by the use of the traditional spinning process are limited.
To solve the above question, Chinese patent application Publication No. CN1225960 discloses an immersion method, in which porous hollow fiber is immersed in a solution of functional materials, thus the fragrance with a low boiling point can be filled into the hollow fiber. U.S. Pat. No. 6,021,822, Chinese application publication No. CN1198196, and the cited references thereof, also disclose a method for encapsulating functional materials into porous hollow fiber using the immersion process, thus many kinds of functional materials with temperature sensitive cannot be composite with the hollow fiber using these processes. Furthermore, when using the above method, most areas of the hollow fiber, and even all of the length of the hollow fiber, should be formed communication pores. Washing is also necessary after filling the hollow fiber to remove the remained functional materials and auxiliary materials on the surface of the fiber. Post processing cannot carry out until washing is performed. Obviously, those processes are relatively complicated. Furthermore, washing will affect, even destroy the functional materials filled in the hollow portion. Therefore, the kinds of functional materials to be filled are still limited; as a result, the kinds of the functional fiber produced with above method are still limited.
U.S. Pat. No. 5,538,735 and Chinese application Publication No. CN1108583 disclose a method of filling drugs or film forming materials into the hollow portion of the fiber using vacuum facilities, comprises the steps of: submerging the fibers in a liquid containing the drugs or film forming materials, placing the submerged fibers in a vacuum chamber, drawing air out of the void of the fiber by withdrawing the air in the vacuum chamber, and drawing the liquid into the void by allowing the air pressure in the vacuum chamber return to the ambient pressure. Some drugs or film forming materials can be incorporated in the hollow portion of the fiber at a room temperature. However, during filling, the hollow fibers are completely submerged in the liquid of filling materials, thus large amounts of filling materials must be used, which cause high cost, particularly for valuable pharmaceuticals, fragrance, or other valuable functional materials. This disadvantage is most outstanding for mass production. Furthermore, this process is not suitable for filling volatile materials because of the evacuation of the vacuum chamber, in which there are liquid containing volatile material. Additionally, washing process is also necessary after filling for the post treatments.
U.S. Pat. No. 4,017,030 discloses a device comprising an elongated capillary conduit having one closed end for absorbing a flower-like odor or insecticide from an open ends thereof by capillary action, thus the follower-like odor or insecticide being incorporated in the device to be released as vapors. However, only such a liquid with a low viscosity can be filled, or the length of the hollow fiber to be filled is limited. When the filled materials have a high viscosity, or a long hollow fiber is filled, this device will not be suitable.
Generally, the process of manufacturing composite fiber is not finished only after the functional materials are incorporated into the hollow portion of the hollow fiber. For making most kinds of functional fiber, a subsequent chemical or physical treatment is necessary to cause physical change or chemical reaction of the filled functional materials or auxiliary materials. Such treatments include curing or gelatinizing the functional materials and auxiliary materials in the hollow portion, thus forming precipitation in the hollow portion or coating at the inner wall of the fiber, and etc. Generally, after the fiber is filled using the immersion or vacuum immersion process, the subsequent treatments cannot be performed without washing the surface of the fiber. However, the functional materials and auxiliary materials filled in the hollow fiber will be easily lost or destroyed during washing, and the property imparted by the functional materials will become reduced in storage or in use since the communicating pores or open ends of the fiber are not sealed yet. Furthermore, filling function materials using capillarity action, not only the filled materials and the length of the fiber are limited, but also the liquid filled in the hollow portion will move during post treatments since one end of the fiber is open, therefore, some segments in the hollow portion of the fiber are out of filling material, and forms voids without filling materials. As a result, a uniformly filled fiber cannot be produced.
In view of the foresaid, the methods described as above can just be applicable when no post treatment is necessary after the functional materials and auxiliary materials are incorporated in the hollow fiber. Moreover, the kinds of functional and auxiliary materials, and the length of the fiber to be filled are limited.
Therefore, an improved method of manufacturing core-sheath composite fiber is desired which overcomes the disadvantages of the prior art.